 
	The querySelectorAll, return the select items as Nodelist object. NodeList is not an Array, it is possible to iterate on it using forEach(). It can also be converted to an Array using Array.from(). (more)
Trigger the event
 
	the e, is the mouse event, to get the actual 'source' element that clicked we use e.srcElement
 
	to get the parent, we using the e.srcElement.parentNode
 
	Put it all together
		JavaScript:
	
	//example of TR
[TR]
	
[TD]  //first TD
		[img]assets/cat_icon.png[/img]
	[/TD]
[TD]  //second TD
		[url='list_topics.php?id=1']Health[/url]
	[/TD]
[TD]2018-06-04[/TD]
[TD]
		[B][/B]
	[/TD]
[TD]  //fourth TD
		<a id="btn_edit" class="btn btn-primary btn-xs">Edit</a>
	[/TD]
[/TR] 
	
		JavaScript:
	
	var tbl_btns = document.querySelectorAll("#btn_edit");
tbl_btns.forEach(function(elem) {
	elem.addEventListener("click", function(e) {
		e.preventDefault();
		var x = getSelected(e.srcElement);
		console.log(x);
	});
});
function getSelected(e){
	//first TD
	var id = e.parentNode.parentNode.cells[0].children[0].getAttribute('data-id');
	
	//second TD
	var forum_name = e.parentNode.parentNode.cells[1].children[0].text;
	
	//fourth TD
	var forum_private = e.parentNode.parentNode.cells[3].childElementCount;
	
	return { id, forum_name, forum_private };
}Optimize more!
		JavaScript:
	
	Array.prototype.forEach.call(document.querySelectorAll('#btn_edit'), function(el) {
	el.addEventListener('click', function(e) {
		e.preventDefault();
		var x = getSelected(e.srcElement);
		console.log(x);
	})
	
})
function getSelected(e){
	var tr = e.parentNode.parentNode;
	var id = tr.cells[0].children[0].getAttribute('data-id');
	var forum_name = tr.cells[1].children[0].text;
	var forum_private = tr.cells[3].childElementCount;
	
	return { id, forum_name, forum_private };
}greets to https://plainjs.com/ and joyrexus
